1. Field of the Invention
The present invention relates to a signal receiver which can be effectively used for a tuner of a television receiver.
2. Description of the Prior Art
In television broadcasting, amplitude modulation (hereinafter referred to as "AM") is used in the terrestrial broadcasting systems, and frequency modulation (hereinafter referred to as "FM") is utilized in the satellite broadcasting systems. A typical conventional television receiver has an AM signal demodulator for reception of terrestrial broadcasting and no FM signal demodulator is incorporated therein. Accordingly, in order to receive satellite broadcasting, an additional special-purpose receiver unit (i.e., an FM signal demodulator) must be connected to the television receiver.
Examples of the conventional special-purpose receiver units include the external adapter type as shown in "SHF Direct Satellite Broadcasting Receiver", Y. Shiomi et al., National Technical Report, Vol. 30, No. 1 FEB, 1984, pp. 4-12 and the built-in type as shown in "Toshiba Television With Built-In BS Tuner 21V230", Television Technics & Electronics, Vol. 32 No. 9, September 1984, pp. 30-35 .
These prior arts suffer, however, from a high degree of redundancy in the circuit configuration, high production cost and large circuit size because two different kinds of receiving systems are employed to receive satellite broadcasting and terrestrial broadcasting, respectively.